The present invention relates to a system for replacing mold blocks in a moving mold tunnel molding apparatus. According to the present invention, the mold blocks are replaced without interrupting operation of the molding apparatus.
Molding apparatus, such as pipe molds, have mold blocks which continuously move around an endless track. On one side of the track the mold blocks are in a closed condition to form a moving mold tunnel where product is shaped within the molding apparatus. The mold blocks open at the downstream end of the tunnel to release the product and are then recirculated back to the upstream end of the mold tunnel.
There are currently two different styles of molding apparatus having moving mold tunnels. According to one of these styles which is known as a clam shell type molder, a pair of mold block sections are mounted on a common carrier which circulates around a single looped track. The mold block sections hinge to open and close relative to one another on opposite sides of the track.
The other style of moving mold tunnel apparatus is formed by a pair of endless tracks and the mold blocks are formed by mold block sections mounted on carriers of the two tracks. The two tracks have track portions which extend side by side parallel with one another where the mold block sections from the two tracks meet to form the moving mold tunnel.
In the past, it has been necessary for mold block replacement to stop movement of the mold blocks in a moving mold tunnel type apparatus. According to prior art replacement methods the mold blocks must be stationary in order to release them from the track and replace them with new mold blocks.
This known method of mold block replacement results in a number of drawbacks. Firstly, it is time inefficient in that the molding operation must be shut down during the replacement. Secondly, it can result in hazardous conditions as a result of the shut down. Specifically, when the shut down occurs, there is a possibility of dangerous plastic build up in the extrusion equipment which must be cleared before the extrusion equipment can be started up again.
The present invention provides molding apparatus having a moving mold region in which mold block replacement is carried out without having to interrupt operation of the molding apparatus.
In particular, the molding apparatus of the present invention, which is used in a continuous molding operation, comprises looped endless track means, track carriers which are moved around said track means to and from a product shaping mold region, and a transfer system for replacement of mold block members used in the apparatus without interrupting the molding operation. The transfer system comprises transfer carriers controlled to move synchronized with the track carriers at a transfer location remote from the mold region and means to slide the mold block members between the track carriers and the transfer carriers at the transfer location.